Apparatus for uniformly heating noncircular outlines



Aug. 25, 1959 H. w. LEIGHTON 2,900,762

' APPARATUS FOR UNIFORMLY HEATING NON-CIRCULAR OUTLINES Filed D60. 23, 1955 Fig. 2

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A TTORNEYS United States Patent.

APPARATUS FOR UNIFORMLY HEATING NON- CIRCULAR OUTLINES Herndon W. Leighton, Montelair, N.J., assignor to Allen B. du Mont Laboratories, Inc, Clifton, N.J., a corporation of Delaware Application December 23, 1955, Serial No. 555,115

2 Claims. (Cl. 49-2) This invention relates to an apparatus for making rectangular cathode ray tubes having metal sides, and particularly to an apparatus for sealing a rectangular glass faceplate to the metal funnel of such tubes.

In the art of sealing round glass faceplates to conical metal funnels, it is the usual practice to position the faceplate in the mouth of the funnel and to rotate the entire assembly in front of gas heaters to obtain uniform heating of the area of contact, or seal area, which exists between the faceplate and the .sealing ledge of the metal funnel.

In a rectangular cathode ray tube, theglass faceplate is not round, but has a substantially rectangular outline. have a sealing ledge which is also substantially rectangular. In sealing rectangular metal funnels to rectangular glass faceplates, a problem arises in that the gas burners must be sufficiently distant from the axis of rotation to clear the corners of the rectangle, and yet must provide suflicient and even heat to the entire sealing area without overheating or underheating the corners.

It is known that the temperature within a gas flame varies considerably from one part to another, and that the hottest part is just beyond the-tip of the flames inner cone. In order to keep the rectangular sealing ledge exposed to the hottest part of the flame as the funnel rotates, it has been the practice heretofore to move the burners in and out mechanically according to the rectangular contour of the faceplate. However, this mechanical movement requires a considerable force since a large number of burners must be radially moved in synchronism. As an alternative, it has also been pro posed heretofore to incorporate a large number of stationary gas burners which are directed toward the center of rotation. All of these burners are kept at a uniform setting to establish a uniform flame length on the theory that during rotation the longer sides of the rectangular sealing ledge are exposed to the hottest flame portion for a relatively short time, and the corners of the sealing area are exposed to the cooler flame portions for a longer interval. Since such an arrangement tends to be a compromise, it has the disadvantage of providing an optimum heat for only certain sections. of the sealing area while simultaneously overheating some sections and underheating other portions.

The present invention contemplates the control of the instantaneous flame-length by adjusting the flow of the fuel-gas, oxygen, or both. As a particular section of the sealing ledge passes in front of each burner, the flamelength of that burner is adjusted so that the hottmt portion of the flame playson the sealing ledge. A cam serves as the controlling means which, in turn, energizes the flow-adjustment valves.

One object of this invention is to provide an improved apparatus for sealing rectangular glass faceplates to matching metal frames.

Another object is to provide an apparatus for adjusting the flame-length of gas burners, in accordance with The mouth of the metal funnel therefore must ice I the varying distance between the end of the gas burner and the proximal point of the sealing ledge of the rectangular metal funnel.

Further objects will become evident after studying the following specification, together with the drawings, in which: 7

Figure 1 shows sealing apparatus constructed according to the invention;

Figure 2 shows a top view of the apparatus of Figure 1; and a I Figure 3 shows a modification of the apparatus in Figure 1 for making rectangular envelopes to be used in the manufacture of color television cathode ray tubes and the like. 7

To make a rectangular metal cathode ray tube, a metal funnel is used whose sealing area is also of rectangular configuration. According to this invention, the funnel is placed in a holder which is rotatable about the funnel axis, and a matching rectangular glass faceplate is then placed on the sealing ledge. Several gas burners, each fixed in position around the periphery of the sealing ledge, are aimed generally at the center of rotation with their flames playing on the sealing ledge. Each burner is connected to a source of fuel-gas and to a source of oxygen (either pure oxygen or air) through individual supply pipes which are provided with individual valves to control the flow of oxygen. The rotatable holder includes means which provide a cam-like action to operate mechanical linkages connected to'the valves. Increasing the amount of oxygen causes the flame to shorten, while a decrease of oxygen permits flame lengthening. Conversely, a larger supply of fuel-gas lengthens the flame while less fuelgas would shorten it. Proper adjustment of the flow of the gas and/or the oxygen, permits the flame-length to be readily controlled. By controlling the flow of the gasses in accordance with the rotational position of the rectangular tube, the lengths of all the flames are always adjusted to the optimum length to maintain the sealing ledge substantially in the hottest part of each flame.

In the apparatus of Figure 1 a rectangular metal funnel 11 having asealing ledge 16 and a previously att-ached glass neck 12 is placed in a holder 13. A glass faceplate 14 which may be spherical, cylindrical, flat, or of any other curvature, is placed on sealing ledge 16.

The holder13 is rigidly attached to a turntable mechanism comprising a plate 18 and some form of bearing, shown here as a thrust bearing 17. The turntable mechanism may be rotated by any convenient means, such as a V-belt 19 and driving pulley 21 which is attached by means of a hollow shaft 24 to the plate 18.

Gas burners 23 are located in fixed positions around the rectangular metal funnel 11 to direct flames 24 at the sealing ledge 16. It will be noted that the flames 24 comprise an inner cone 26 and an outer portion 27. A fuel-gas source (not shown) is connected to burners 23 by hose 28, and the direction of fuel-gas flow is indicated by arrows 29. In order for the fuel-gas to'burn properly, oxygen or 'air must be mixed with the fuel-gas in the burners 23. Oxygen from a source (not shown) is fed to burners 23by means of supply pipes 31a and 31b, and the flow of oxygen through pipes 31 is controlled by valves 32a and 3212. As previously explained, it may be also desirable to control the flow of fuel-gas. This may be accomplished by valves similar to valves 32a and 32b.

The edge of the plate 18 may be cut to substantially the same outline as the outline of the sealing ledge 16,

and then serves as a cam to operate individual cam- I followers 33. Each of these cam-followers 33 is connected to one of the control valves 32 to control the amount of oxygen reaching the respective burners 23 in the cam-plate 18. a

When the rotatable holder 13 is turned so that the long sides of the rectangular sealing ledge 16 face burners 23, cam-plate 18 allows the cam-follower members 33 to retract so that a reduced amount of oxygen passes through valves 32a and 32b. This makes the inner cones 26 of flames 24 sufliciently long to allow the hottest part of these flames to engulf the sealing ledge 16. Alternatively, the amount of fuel-gas may be increased to achieve flame-lengthening. Under some conditions, it may be advantageous to vary the fuel-gas and the oxygen simultaneously.

Conversely, when the rotatable holder 13 is turned so that the corners of the cam-plate 18 are in contact with cam-followers 33, the valves 32 will be opened, thus allowing the passage of an increased volume of oxygen. Flames 24 will therefore be shortened to retract the hottest part of the flame and allow it to play on the corners of the sealing ledge 16. As previously stated, this result may also be attained by controlling the flow of fuel-gas, either independently or in conjunction with the changed flow of oxygen.

In sealing the glass faceplate 14 to the metal sealing ledge 16 it is generally desirable to provide an air cushion to prevent the faceplate from settling as it becomes molten along its edges. A blowpipe 37 is therefore introduced into the neck 12 through a cannulated cork 36. Because of the rotation of the neck 12, the blowpipe is commonly provided with a gas-tight rotating connection 38. The practice is for the operator to control the gas pressure within funnel 11 to support faceplate 14 properly as its edges melt and then fuse to sealing ledge 16. r

if desired, valve 320 may be omitted provided that the supply pipe 31a is connected to the supply pipe 311; on the opposite side of the funnel 11 so that both of the diametrically opposed pipes 31a and 31b may be controlled by a single valve such as 32b.

Figure 2 is a top view of apparatus similar to that shown in Figure 1 and shows more clearly the arrangernent of the burners and the outlines of the cam-plate 18 and the sealing-ledge 16. The apparatus in Figure 2 differs from that shown in Figure l in that the gas burners are grouped into sets 123 and 124, with a single supply pipe for the set instead of separate pipes for each burner.

Figure 2 clearly shows that each of the sets of burners 123 and 124 is spaced an equal distance from the center of the tube. Consequently, when the sealing-ledge 16 is in the position indicated by the solid outline, the flames of sets 124 must be adjusted to be shorter than the flames of sets 123. The adjustment may be made by valves similar to valves 32 in Figure 1 and operated by cam-plate 18 in the same way. It may be noted in passing that although the cam-plate 18 is shown as having an outline identical in shape with the outline of the sealing-ledge 16, such an identity is not necessary. Camplate 18 may, for example, be more nearly circular than the outline of sealing-ledge 16 if it is desired to impart only a slight motion to the valve actuating member 33 which is shown in Figure l or at 133 shown in Figure 2. It has been found to be satisfactory to arrange the burners in sets as shown in Figure 2, and of course such an arrangement is considerably easier to adjust than the mdividual burner arrangement shown in Figure 1.

When the tube is rotated to the position indicated by the dashed line of Figure 2, the flames from burner set 123 are shortened until their inner cones just touch the narrow end-portion, while the flames from burner set 4 124 are lengthened until their inner cones just touch the long sides of sealing-ledge 16.

The apparatus of Figure 1 may be modified as shown in Figure 3 to seal a rectangular glass faceplate to a member 111 which is just the outer end of a metal funnel of a type used for making rectangular metal cathode ray tubes for color-television. The funnel of such a tube is divided into member 111 and another, conical member, which is not shown, for convenience of inserting masking structures, and for other purposes which are not concerned with the invention at hand. The member 111 has a flange 34 which is welded to a matching flange on the other member during assembly of the complete color television tube. Flange 34 is shown as extending radially from the body of member 111 although it is not unusual for the flange 34 to be slightly frusto-pyramidal rather than perfectly radial. In any event, there is no neck into which a blowpipe. may be inserted to regulatethe settling of faceplate 14. Therefore, the structure of Figure 3 is provided with a surface 38 which is shaped to fit rim 34, and to which the rim 34 is secured by means of a number of clamps 39 spaced about the periphery. Surface 38 itself is provided with a con tral opening to which a tube 137 corresponding to a blowpipe is coimected, and this tube is connected through a rotatable gas-tight coupling (not shown) to be controlled by the operator, as in the case of the blowpipe 37 in Figure l. Cam-plate 118 controls the action of cam-followers 133 which regulate suitable control-valves which, while not shown, operate as previously described.

Other modifications of the invention may occur to those skilled in the art, and so the invention should not he considered as being limited to the specific embodimeats shown, but only by the following claims:

What is claimed is:

1. Apparatus for forming a cathode ray tube envelope, comprising a rectangular glass faceplate positioned on a metal funnel having a matching rectangular sealing ledge; rotatable means to hold said metal funnel; a plurality of immovable gas burners spaced around said sealing ledge and positioned to direct flames from said burners at said sealing ledge; a source of fuel gas for said burners; a first set of supply lines connecting said source of fuel gas to said burners; a source of oxygen; a second set of supply lines connecting said source of oxygen gas to said burners; means to adjust the length of flame from each of said burners according to the instantaneous distance between the end of said burners and said sealing ledge so that the tips of the inner cones of said flames always strike said ledge, said means corrprising control valve means in one set of said supply lines, said control valve means acting to control the flow of gas in said valve control line and thus control the length of flame of said burners; and means to control the opening of said valve mean in accordance with the instantaneous position of said metal funnel.

2. The device of claim 1 wherein said last means comprises a cam rotating with said rotatable means, and linkages between said cam and said control valve means.

References Cited in the file of this patent UNITED STATES PATENTS 2,017,423 Walker Oct. 15, 1935 2,113,001 Scott Apr. 5, 1938 2,428,825 Arnoldy Oct. 14, 1947 2,573,266 Melcher et a1 Oct. 30, 1951 2,580,450 Melcher et al. Jan. 1, 1952 2,684,557 De Gier et al July 25, 1954 2,686,390 Williams et al Aug. 17, 1954 

